Mike,
You should be able to lock the fronts first most of the time. Slap an adj prop valve in the rear line and dial some out and you will be a happy man.
Lou
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| Duel MC Conversion - Brake Pedal Position https://mail.slantsix.org/forum/viewtopic.php?t=7235 |
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| Author: | killin5 [ Wed Oct 15, 2003 7:11 am ] |
| Post subject: | Duel MC Conversion - Brake Pedal Position |
After what seams like forever, I finally took the Valiant back on the road last night. It’s been down for not quite a year while I have been sloooooooowly completing a restoration. It’s a 63 Valiant. I have changed from the single pot Master Cylinder to a duel pot MC from a 75 Dart. So here is my question. I have quite a bit more travel in the pedal than I did before. I do get a firm pedal once I push it in all the way so I’m thinking that I have all the air out of the lines. It ends up resting right about equal with the gas pedal. Is this normal? I may just be paranoid because the feel is different. But it never hurts to ask. Thanks, John |
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| Author: | Charrlie_S [ Wed Oct 15, 2003 10:07 am ] |
| Post subject: | |
Check the brake shoe adjustment, might have to tighten it up a little. Had the same situation on my Cuda. Just don't go too tight. |
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| Author: | Mike Andreas [ Wed Oct 15, 2003 11:30 am ] |
| Post subject: | Me too |
I did the same conversion when I converted to KH Disc Brakes and my pedal is about even with the gas when depressed. One thing to check is the MC pushrod. How far do you go in before the the rod hits the inside of the MC? I've heard storys of the pushrod actually falling out of the hole. THAT WOULD BE BAD! Some of the slack might be in the shoe adjustment. Some might be weakened hoses though it's probably air in the lines. Someone makes an adjustable length pushrod kit. I know I've seen it but I can't remember where. I have 215 60 14's on the front of my car. I can PUSH HARD and not lock up the fronts. I stop hard but on dry pavement I can't lock them up. I wonder how much braking I'm missing out on. It's WAY better than the 9" drums I replaced. Mike |
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| Author: | Dart270 [ Wed Oct 15, 2003 2:32 pm ] |
| Post subject: | |
Mike, You should be able to lock the fronts first most of the time. Slap an adj prop valve in the rear line and dial some out and you will be a happy man. Lou |
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| Author: | Mike Andreas [ Wed Oct 15, 2003 2:58 pm ] |
| Post subject: | I already do |
I installed at MP valve in the rear line from the start. I can't lock the rears either the way it's setup now. I dialed out the rears gradually until they didn't lock before the fronts. I basically stopped when they didn't lock. Maybe I need a smaller ID Master Cyl. I haven't worked on the brakes for a couple of years. Maybe it's time for a complete checkup. 
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| Author: | '65 Dutch Dart [ Wed Oct 15, 2003 4:42 pm ] |
| Post subject: | |
Mike, I have the same in my car. Kelsey Hayes 4pistons with a Prop. valve. I cannot lock the front wheels, not even if I adjust the rear right. But I had the fronts checked and the outcome was they were working just fine,... Just so you know. And about the rod falling out, this usually happens when you use a master cilinder which is meant for use with a booster, without the booster ( Master directly onto the firewall) that's all from me 
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| Author: | Pierre [ Wed Oct 15, 2003 5:03 pm ] |
| Post subject: | |
I am currently upgrading to KH discs. I asked for a MC from a 71 duster with regular discs, and the listing came up with a 1 1/32" MC. Hopefully soon I will get the original proportioning valve / distribution block from the 71 that the rest of the parts came from. The master cylinder came with a small rubber grommet type deal where I believe you are supposed to put it around the rod before you install it in the master so it will wedge the rod in the MC and it won't fall out. When I took out the drum MC that was in there this rubber grommet wasn't there. I could be wrong maybe that grommet has another use, but somewhere I remember reading something about rod retainers. |
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| Author: | Craig [ Wed Oct 15, 2003 9:06 pm ] |
| Post subject: | |
That rubber thing fits into a groove the MC piston first, then the rod snaps in through the rubber thing. |
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| Author: | Craig [ Wed Oct 15, 2003 9:09 pm ] |
| Post subject: | Re: Me too |
Quote: ....... One thing to check is the MC pushrod. How far do you go in before the the rod hits the inside of the MC? I've heard storys of the pushrod actually falling out of the hole. THAT WOULD BE BAD! ..............
Mike You should not have any travel of the pushrod in and out of the MC piston. The rubber retainer ring should hold it in all the way at all times. |
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| Author: | Pierre [ Wed Oct 15, 2003 9:13 pm ] |
| Post subject: | |
Craig, wow thanks good to know! I guess whomever replaced the MC years ago never put it in. It was around the bar that holds the lid down. I find no mention of this ring in the service manual though, strangely enough. I'll have another look. Edit: Nope.. the book states in the removal section to disconnect the rod from the pedal and remove it with the master cylinder. In the breakdown diagrams they don't show it. In the bleeding section it tells you to push on the piston with a wooden rod, and shows a picture of the rod touching the piston directly. Wierd... |
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| Author: | mpgFanatic [ Thu Oct 16, 2003 6:43 pm ] |
| Post subject: | Re: Duel MC Conversion - Brake Pedal Position |
Quote: It’s a 63 Valiant. I have changed from the single pot Master Cylinder to a duel pot MC from a 75 Dart. So here is my question. I have quite a bit more travel in the pedal than I did before. I do get a firm pedal once I push it in all the way so I’m thinking that I have all the air out of the lines. It ends up resting right about equal with the gas pedal.
No, it's not normal. I just replaced my single with a dual, and the pedal is exactly where it was before: delightfully high. Total travel might be about an inch, then it's like standing on a rock.Is this normal? In addition to the other good suggestions about adjusting the shoes, I would verify that the new MC is designed for a 4-drum application. It sounds like the diameter of the new MC bore might be different than the diameter of the one you took out. - Erik |
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